1. Field of the Invention
The present invention relates to a die for manufacturing honeycomb bodies used for extruding honeycomb structural bodies.
2. Description of Related Art
Generally, various kinds of dies for manufacturing honeycomb bodies are known, which comprise; a die main body including batch supply holes which are opened to a backside surface of the die, slit channels which are communicated with the batch supply holes and are opened to a foreside surface of the die and a taper worked portion which is formed by working an outer peripheral portion of the foreside surface of the die in a taper manner; and a control plate arranged at a portion opposed to the taper worked portion.
FIG. 3 is a schematic view showing one embodiment of a known die for manufacturing honeycomb bodies. In the embodiment shown in FIG. 3, a die 51 for manufacturing honeycomb bodies comprises a die main body 52 and a control plate 53. The die main body 52 has a disk-shape and comprises batch supply holes 61 which are opened to its backside surface (lower surface (not shown) in FIG. 3) and slit channels 62 which are opened to its foreside surface (upper surface in FIG. 3). The slit channels 62 have a crisscross shape at the foreside surface of the die main body 52, and the batch supply holes 61 are communicated with alternate intersection points. An outer peripheral portion of the die main body 52 is worked into a taper shape to form a taper worked portion 63. The control plate 53 is connected to the die main body 52 via a spacer 64 in such a manner that one surface 53a is opposed (parallel in FIG. 3) to the taper worked portion 63.
In the die 51 for manufacturing honeycomb bodies having the construction shown in FIG. 3, a ceramic batch for example is supplied from the batch supply holes 61 which are opened to the backside surface of the die 51, and the thus supplied ceramic batch is extruded from the slit channels 62 which are opened to the foreside surface of the die 51, so as to obtain a honeycomb structural body. Then, it is possible to reduce an inward batch stress when an outer wall is formed and to prevent a collapsing of outer cells i.e. a generation of wrinkle portions in the honeycomb structural body by forming the taper worked portion 63 at the outer peripheral portion of the die main body 52 and by arranging the control plate 53 at a portion opposed to the taper worked portion 63.
However, if a thin wall honeycomb structural body having a thin rib thickness, which is required recently, is to be formed, an isostatic strength of the honeycomb structural body become smaller correspondingly since the rib thickness is thin. As a result, there is a drawback such that it is necessary to take care of a handling of the honeycomb structural body. In order to eliminate the drawback mentioned above, it is thinkable in the die 51 for manufacturing honeycomb bodies having the construction shown in FIG. 3 that a space between the taper worked portion 63 and the control plate 53 is widened by making a thickness of the spacer 64 thick so as to obtain a honeycomb structural body having a thick outer wall. However, if the thick outer wall is to be formed in this manner, a batch is supplied in excess at this portion to an extent such that the outer wall becomes thicker. In addition, when the outer wall is formed, a pressure of the batch moving between the taper worked portion 63 and the control plate 53 becomes large and is applied in an inward direction of the honeycomb structural body. As a result, there is a drawback such that outer ribs are deformed and a collapsing of the outer cells i.e. a wrinkle portion is generated.